Method of manufacturing a heat exchanger



Jan. 21, 1969 A. E. PLEGAT 3,422,777

METHOD OF MANUFACTURING A HEAT EXCHANGER Filed May 25, 1964 Sheet of 5 mve NTOR ALAIN E. PL EGAT I Jan. 21, 1969 A. E. PLEGAT METHOD OF MANUFACTURING A HEAT EXCHANGER Sheet Filed May 25, 1964 Fiat). JLLLLLA HHHHIH INVENTOR ALAIN E. APLEGAT.

Jan. 21, 1969 A. E. PLEGAT METHOD OF MANUFACTURING A HEAT EXCHANGER Sheet Filed May 25, 1964 Fia'l'l.

INVENTOR ALAIN E.

PLEGAT United States Patent US. Cl. 113118 Int. Cl. B21d 53/04 9 Claims In numerous applications, it is necessary to use, more particularly as heat dissipators, gille d metal elements which are put into thermic contact with the heat generating component or components. According to the nature of these components, the heat exchanger elements must possess particular characteristics, especially with regard to their contact surface with the heat producing components. It is also necessary that their thickness varies according to the more or less large quantity of heat to be dissipated.

Up till now, it has been necessary to make these heat exchanger elements by means of metal sections, more particularly obtained by extrusion, after the computations defining their particular characteristics have been made.

These known elements generally give satisfaction from the technical standpoint but they have the disadvantage of being expensive, more particularly when it is necessary to produce heat exchanger elements intended to be adapted to particular members, as is the case in electronic industries where it is necessary to be able in particular suitably to cool semi-conducting appliances, lamps, etc.

The present invention relates to a new method of making a heat exchanger element whose particular construction enables it to be adapted at will and has the advantage of an extremely low cost price.

According to this invention, the method of making a heat exchanger element utilizes a continuous thin, resilient metal strip, that is caused to pass between shaping components imparting regular corrugations thereto, whose height and width are very much greater than the thickness of said strips, said height of the corrugations being preferably about 100 times the thickness of the strip and said width of the corrugations being about 10 times the thickness of the strip, and the shape of the corrugations being also chosen so that several identically corrugated strips, but the width of which may be different, are juxtaposed by fitting in their corrugations, so that finally an element is obtained whose wall thickness is adapted to previously define utilization conditions.

Various other characteristics of the invention will moreover he revealed by the detailed description which follows.

Embodiments of the invention are shown by way of non-restrictive examples in the attached drawings.

FIGURE 1 is a diagrammatic perspective showing one embodiment of the method of the invention.

FIGURE 2 is a perspective of a part of an exchanger element obtained according to the invention.

FIGURE 3 is a section on a larger scale, taken substantially along the line III-III of FIG. 2.

FIGURES 4, 5 and 6 are partial perspectives on a larger scale, showing particular characteristics of the invention.

FIGURE 7 is a plan showing a first method of applying the invention.

FIGURE 8 is a section taken substantially along the line VIIVII in FIG. 7.

FIGURE 9 is an elevation of a second method of applying the invention.

FIGURE 10 is a diagrammatic elevation in section corresponding to FIG. 9.

3,422,777 Patented Jan. 21, 1969 "ice FIGURE 11 is a plan illustrating another application of the invention.

FIGURE 12 is a cross section corresponding to FIG. 11.

FIGURE 13 is a cross section of another application.

According to the invention for making the heat exchanger element, more particularly a heat dissipator, it is advantageous to proceed as shown in FIG. 1, according to which a metal strip 1 is used as raw material. This strip can be made from copper, aluminium, brass, steel or other metal or an alloy, possibly covered with other metals or some products. This strip is subjected to a shaping operation, preferably continuous, for example by means of a set of shaping wheels 2 or press tools which impart thereto corrugations 3 of regular pitch, whose height h and width 1 (FIG. 2) are great in comparison to the actual thickness of the strip. For example, the thickness of the strip will be about 0.10 mm. for a corrugation height of about 10 mm. and a width of said corrugations of about 1.5 mm. In addition to corrugations 3, stampings 4 are advantageously formed, as shown in FIGS. 2. and 3, in the sides of corrugations 3, these stampings being able advantageously, as can be seen in FIG. 3, to define cuts 5 and wedges 6 intended to define particular paths for air currents or other fluids that must be caused to circulate in corrugations 3. The shape of the stampings 4 and their arrangement are chosen so that they are able to be mutually inserted when the contiguous folds 3a, 312 (FIG. 2) are brought together until they come into contact, as occurs in certain methods of applying the elements of the invention.

By way of example, FIG. 3 shows the wedges and cuts enabling this result to be obtained. Actually, each fold has a series of wedges 6a directed to the left, and a series of wedges 6b directed to the right, these wedges being respectively separated by cuts or recesses 5a in which the corresponding wedges of the contiguous folds can be inserted. The amplitude that the wedges project is also preferably great in relation to the thickness of the material of which the strip 1 is made, for example, in a ratio of 1 to 10, so that the recesses 5 do not risk becoming blocked up even when wedges are inserted therein, so that fluid currents can freely circulate while following, for example, a progress as shown by the arrows 1, (FIG. 3). Owing to this regular symmetrical arrangement of the stampings forming the wedges and recesses, or otherwise, it becomes possible to bring together some of the folds 3, 3b of an element until they come into contact, and also to juxtaposeand this is an important characteristic of the invention-several corrugated strips 1, 1a, 1b, as shown in FIG. 4, which enables an element to be obtained whose thickness is obviously a multiple of the thickness of the basic element, produced by the device of FIG. 1. Actually, the strip 1 being of metal has a certain resilience, and the thickness of this strip being slight in comparison to the amplitude of the corrugations that are imparted thereto, when several thicknesses of the strip are inserted one in the other, as shown in FIG. 4, there results then a mutual distortion of the various strips, this distortion being, however, slight, and within the limit of the resilient distortions that can be accepted. On this account, the strips 1, 1a, 1b which are mutually inserted in one another, exert a resilient pressure on each other which keeps their surfaces in close contact. Also, the particular symmetrical arrangement, described above, of the stampings formed with wedges and recesses also permits the latter to be mutually inserted in each other resulting in a new dissipator of homogeneous composition, and consequently, whose heat transmission characteristics can be easily adapted according to requirements. As can be seen from the foregoing, the product finally obtained according to the invention is always made from the same basic element, namely, a corrugated strip of constant thickness, made continuously, whose folds mutually correspond and can, according to requirements, be more or less separated by elongation, or on the contrary, brought closer together by compression, according to the quantity of heat to be dissipated.

Whileutilizing the same basic folding, namely, for example, that according to FIG. 1, which always imparts the same shape to the strip 1, it is still possible for producing the heat conducting element, to take advantage of an additional variable which consists in forming, with the same tool equipment, strips of various Widths L, L (FIG. In this manner, strips 1, 10, etc., respectively having the widths L, L etc., can be juxtaposed so that the resultant product has a greater thickness in some places than in other places. Adaptations according to FIGS. 4 and 5 can moreover be combined.

FIG. 6 shows that an additional characteristic can be imparted to the dissipator of the invention. Actually, according to that figure, the making of wedges 6 on the folded part is shown, these wedges projecting outwardly so as to form resilient bearing lugs intended, as shown in the following to facilitate heat transmission in certain applications between a cooling component and the dissipating element of the invention.

Although in most cases unnecessary, it is also possible according to the invention, to completely link together the various juxtaposed strips forming the exchanger. When the strip is made of aluminium, it can, previous to its shaping, be covered on at least one of the faces thereof by a brazing product, for example, an aluminiumsilicon alloy; likewise, said strip, when made of copper, brass or steel strip, can be coated with a soft solder, for example, a tin alloy, and it then becomes possible, by heating, either in a furnace or by a flame, or in a bath of a flux, according to the kind of metal of which the strip is made, to effect a continuous solder whose operation can be carried out without any manual work, since the juxtaposition itself of the various strips is easily carried out by means of forming wheels placed upstream the furnace or bath in which the assembled strips must then pass to be soldered. The connection and possibly protection from corrosion can also be insured by a glue or a heat conducting varnish.

The applications of the article thus obtained are obviously multiple and in fact apply to most of the cases in which a heat transfer must be obtained between two fluids, as well as in most cases in which the heat produced by an appliance must be dissipated. According to the invention, the heat exchanger element is most particularly applicable to the cooling of electric or electronic apparatuses and more particularly to the cooling of semiconductors, to gas or vacuum tubes, etc. Such applications, in which the special qualities of the element of the invention are most particularly revealed, appear in the drawing.

In FIGS. 7 and 8 is shown a platen 7 made from a heat conducting material on which a transistor or transistors 8 are mounted. The platen 7 is provided on each of its two faces with a segment of corrugated strip 1, formed by the juxtaposition of any required number of basic strips and which is fixed on the platen by any suitable means, for example, by soldering or adhesion. The heat given off by transistor 8 is thus transmitted to platen 7, then to the strip 1 which dissipates the same to the atmosphere. Owing to the corrugated arrangement of the strips, air can be blown in the direction of the arrows f into the ducts and conduits defined by said strips, and an optional hooding 7a, which still further activates cooling. In an arrangement of this kind, the use of the exchanger of FIG. 5 is particularly appropriate, since it is obvious that the hottest part of the platen 7 is that in the vicinity of the transistor 8 and it is therefore advisable that the corrugated strip should have its thickest part in the immediate proximity of said hottest part. Moreover, as a function of the amount of heat provided which must be given off, it is possible to adapt the heat dissipating element, by more or less tightening the corrugation thereof, i.e., by causing the width 1 to vary that separates the various folds of the strip.

According to FIGS. 9 and 10, a lamp 9, of glass, for example, is shown, diffusing considerable heat. In this case, the corrugated strip 1 is wound around said lamp in the manner of a cylindrical exchanger, and its terminal corrugations shown at 1 are inserted one in the other, which forms a self-fastening. It is particularly appropriate in this embodiment to use the strip having the additional characteristic of FIG. 6, for, owing to the resilience of the wedges 6 the heat dissipating element is kept closely applied against the wall of lamp 9, which insures an excellent thermic connection between said wall and the various corrugations of the dissipating element. The thickness of the heat dissipator is chosen according to the number of thermal units to be dissipated by utilizing an appropriate number of corrugated strips stacked as explained with reference to FIG. 4 or FIG. 5.

Another arrangement is shown in FIGS. 11 and 12, according to which the invention applies to the cooling of a transistor 10 which is mounted on a circular shaped platen 11. In this case, a segment of corrugated strip is prepared and its two ends joined by self-fastening, as described above with reference to FIG. 9, then the cylinder obtained is distorted by making its generatr-ices pivot around one of the ends thereof, so as to form a crown 1 which is attached to platen 11 and possibly resiliently tightened by its inner part 1 right round transistor 10. A hooding 11a can cover crown 1 to facilitate the passage of a jet of cooling air blown in the direction of the arrows. Another Way of describing the crown is to state that the stacked and fastened strips are folded about their upper or lower edges to turn the passages Within the corrugations 90.

Numerous other examples of applications of the element of FIGS. 1 to 5 can be imagined without going outside of the scope of the invention. In particular, this element 1 can, if so desired, be spirally wound as shown in FIG. 13 around a tube 12 inside and/or outside the latter.

The invention is not restricted to the forms of embodiment shown and described in detail, for various modifications can be applied to it, without going outside of its scope.

I claim: 1. A method of making adaptable heat dissipators for various objects to be cooled, comprising the steps of form.-

ing identical transverse corrugations in a plurality of thin 2. A method of making adaptable heat dissipators for various objects to be cooled, comprising the steps of forming identical transverse corrugations in a plurality of thin metal strips having substantially the same thickness to delimit parallel folds therein, said corrugations having a height and pitch which are much larger than said thickness of the strips, stacking a plurality of the corrugated strips to form a heat exchanger having a predetermined thickness and so that the corrugation folds of the strips are nested and slightly, elastically distorted by engagement of the fold surfaces of adjacent strips against one another, and stretching the stacked strips while fixing them to an object to be cooled.

3. A method as set forth in claim 2 comprising the further steps of providing said strips on one at least of the surfaces thereof with a fusible material having a melting temperature lower than the melting temperature of the metal forming said strips, and heating the stacked strips to the melting temperature of said fusible material while fixing them to the object to be cooled.

4. A method as set forth in claim 2 wherein said plurality of metal strips are selected of different widths, and the identically corrugated strips are stacked in order of progressively decreasing width.

5. A method as set forth in claim 4 in which during stacking of said strips of decreasing width, one lateral side of each strip is aligned with the same lateral side of the other strips.

6. A method as set forth in claim 2 comprising the further steps of cutting and bending lugs in said metal strips in the portions of the corrugations which are bent to form successive folds, so as to cause the lugs to protrude from the heat exchanger, and pressing said lugs against the object to be cooled while fiXing the exchanger to said object.

7. A method as set forth in claim 2 comprising the further steps of cutting and bending wedges in said metal strips in the portions of each corrugation extending between the folds, whereby when said strips are stacked said wedges form air passages and pertubators for flow of air transversely of the strips on both sides of each corrugation.

8. A method as set forth in claim 2 comprising the further steps of cutting said stacked strips to a given length segment, rolling sa-id segment to substantially cylindrical shape for closely fitting about a cylindrical object to be cooled, mutually inserting the end corrugations of said segment in one another to secure the ends of the strips together, and fitting said segment on said cylindrical object to be cooled.

9. A method as set forth in claim 8 comprising the further step of distorting said cylindrical segment after insertion and securement of the end corrugations by folding the segment around one of its edges, whereby the passageways formed by the corrugations are turned and the segment is shaped as a crown, and securing said segment to said object to be cooled in such a way that said object is at least in part engaged with the inner surface of said crown.

References Cited UNITED STATES PATENTS 1,749,342 3/1930 Hazen 72196 1,826,344 10/1931 Dalgliesh 1l3118 2,001,553 5/1935 Spencer 72-196 3,083,662 4/1963 Zeidler l131l8 3,160,132 12/1964 Mowatt ll3ll8 2,571,505 10/ 1951 Waldron 16-5l83 3,002,729 10/1961 Welsh -183 FOREIGN PATENTS 636,300 2/1962 Canada.

CHARLES W. LANHAM, Primary Examiner.

L. A. LARSON, Assistant Examiner.

US. Cl. X.R. 

1. A METHOD OF MAKING ADAPTABLE HEAT DISSIPATORS FOR VARIOUS OBJECTS TO BE COOLED, COMPRISING THE STEPS OF FORMING IDENTICAL TRANSVERSE CORRUGATIONS IN A PLURALITY OF THIN METAL STRIPS HAVING SUBSTANTIALLY THE SAME THICKNESS TO DELIMIT PARALLEL FOLDS THEREIN, SAID CORRUGATION HAVING A HEIGHT AND PITCH WHICH ARE MUCH LARGER THAN SAID THICKNESS OF THE STRIPS, AND STACKING A PLURALITY OF THE CORRUGATED STRIPS TO FORM A HEAT EXCHANGER HAVING A PREDETERMINED THICKNESS AND SO THAT THE CORRUGATION FOLDS OF THE STRIPS ARE NESTED AND SLIGHTLY, ELASTICALLY DISTORED BY ENGAGEMENT OF THE FOLD SURFACS OF ADJACENT STRIPS, AGAINST ONE ANOTHER. 